Clorimeter.



1 G. NUTTING.

COLORIMETER.

APPLICATION mum JAN.1'I, 1012.

Patented May 21, 1912.

3 SHEETS-SHEET 1.

P. G. NUTTING.

COLORIMETER.

APPLICATION TILED JAN.17, 1912.

Patented May 21, 1912.

3 SHEETS-SHEET 2.

P. G. NUTTING.

GOLORIMETER.

APPLICATION FILED JAN.17. 1912.

Patented May 21, 1912 3 SHEETS-SHEET 3.

' UNITED STATES PATENT OFFICE.

PERLEY GILMAN NUTTING, OF WASHINGTON, DISTRICT OF COLUMBIA.

Specification of Letters Patent.

- cononmn'rnn.

Patented'May 21, 1912.

Application filed January 17, 1912. Serial No. 671,756.

. nnmca'rrm r rim PUBLIC.)

To a l whom it may concern:

Beit known that I, PERLEY GILMAN NUT- TING, a citizen of the United States of America, and a resident of Washington, in the District of Columbia, have invented a new and useful Improvement in Colorimeters, and application for Letters Patent on said improvement is made under the act of Congress of March 3, 1883, chapter 143.

' clear and exact specification of my improvement, such as will enable those skilled in the art to which it appertains to make and use the same.

This invention relates to apparatus of the type used for determining uniquely the character of an unknown light. As is customary in apparatus of this kind, the

- character of the emitted, transmitted, or reflected light is determined by comparing it with light of known character.

The'invention relates more particularly to a colorimeter, not for measuring the percentage composition of red, green and blue (trichromatic analysis), but for ascertaining the wave-length of the dominant hue or its complementary, together with the paleness of this hue: that is, the percenta e of white light which is mixed with the lig t of the dominant hue. This may well'be termed monochromatic analysis. My complete apparatus includes also a photometer of some known type, for measuring the intensity and luminosity of the unknown light So far as I am aware, the practical colorcomposition-measuring instruments hereto fore designed have all been polychromatic: that is, the known light has been composed of rays passed through or reflected from a plurality of'screens each of known color and paleness. Examples of such apparatus are found in the United States patents to Fajita, 961,852; to Ives, 894,654; in the German patents to Kallab, Nos. 193814, 198449. 205271,-220184 and 221413 ;-.',i n Circular No. 28 of the United States Bureau of Standards (Washington, Government Printing Office, 1911) and in text books on color.

Examples of (impractical) monochromatic instruments for matching color are found in Abneys Colour Measurement and Mimture (New York, E. & J. B. Young & (30., 1891).; and in the Arons chromoscope, described in Annalen der Pkg silo, vol. 33, pp. 799-833.

The object of the. invention is to embody a method of color measurement .which shall be free from arbitrary reference standard screens or surfaces, 'in an apparatus whose adjustments and readings may be made with ease and exactitude.

Other, objects of my invention will more fully hereinafter appear and the novel. features of the invention will then be pointed out in the appended claims. Referring now to the diagrammatic drawings, wherein like reference characters represent like parts throughout the several views,

Figure 1 is a Maxwell color triangle, illustrating graphically the difi'erence between the trlchromatic analysis of the prior art and my system of monochromatic analysis. Fig. 2 is a'plan of my apparatus in one position, with a photometer. Fig. 3 shows the field viewed at E, with the arrangement illustrated'in Figs-2, 4 and 5. Fig. 4 is a view in perspective of parts of the apparatus, looking in'the' direction of arrow 4, Fig. 2. Fig. 5 is a view similar to Fig. 4, showing the parts in a different position. Fig. 6 1s a'plan similar to Fig. 2, showing two positions of collimator B. Fig. 7 shows the field viewed at E, with the arrangement illustrated in Fig. 6.

Referring to the Maxwell color triangle, RGB, Fig. 1, the location of the points: representing the unknown spectral light X, is determined, according to the trichromatic analysis of the prior art, by measuring the intensities of the red, green and blue in the light of unknown color, these intensities being indicated by the relative len hs of the trilinear coordinates w r, w g, an tab. The size of the triangle indicates theabsolute intensity of the unknown light. Instead of the triline'ar coordinates of thepoint m I determine the polar coiirdinates a, and Wan. The angle a between the radius vector Wm,

and a suitable reference line W0 is a measure of the dominanthue of the light X,. The length of the radius vector Wm. reprethe determination is made of the supplementary a of the angle u that is, if the unknown light is purple, hereinafter designated as X,,, the wave-length of the supplementary (represented by a is measured.

limators each comprising a source of light L, a slits for adjusting the amount of light entering the tube It, a pair of nicol prisms n, n, for dimming the light to the desired extent, and a lens Z. O is an observing device .comprising a tube t, a lens Z and a slit 8.

The eye of the observer is at E. P is a dispersing prism. C is a Lummer-Brodhunphotometer cube. White light from collimator M traverses the dispersing prism P and the part of it traversing also the central portion of cube C enters the observers eye at E. Since but a narrow portion H of the spectrum made by prism P and traversing the lens Z reaches the eye through the slit 8, the observer sees the whole inside portion of the field (Fig. 3) of but one hue..

By rotating collimator M about a vertical axis through the center 72 of prism P, pure spectral light of any desired wave-length may be obtained at E. A-' second position of collimator M is shown in dot-ted lines at M, Fig. 2.

In practice the six classes of unknown light are: I, emitted spectral light; II, transmitted spectral light; III, reflected spectral light; IV, emitted purple light; V, transmitted purple light; VI, reflected purple light. As these six classes of unknown light require difi'erent adjustments of the apparatus, they will be considered separately.

.Ca'se I. The arrangement for emitted spectral light is shown in Figs. 2, 3 and 4, except that the screen D is not used in this case. At L (collimator A) is placed the source Whose emitted light X, is to be tested. The part of the light X whichis reflected in the cube C constitutes the outer portion of the field (Fig. 3) viewed at'E.

The known light is-composed of light H of sultable wave-length" from collimator M plus white hghtW from collimator B, totally refiected at the second face 1 of prism P. The

intensities of lights II and W may be ad-v position of the collimator Mor by means of a small auxiliary hand spectroscope (not shown) held at the eye slit 3. The intensities of lights X NV and H are determined from (1) the width of slits s; or 2) the angle between nicols n, or (3) most precisely by using a photometer such as the .lVhit-man disk D, rotated about its axis Gr (by suitable means not shown), together with the standard lamp K. This enables the light X. to be uniquely specified by: (1) the wave-length of its dominant hue,

: which is the wave-length of light H; (2) Referring to Fig. 2, A, B and M are colthe ratio of intensity of light WV to light H;

(3) the luminosity, stated usually in meter candles,-determined as indicated above.

Case II. With transmitted spectral light, a. source of white light is'used at L (collimator A), and the unknown light X, is the light transmitted from collimator A through the screen D to be tested. The rest of the operation is as in case I.

Case III. WVith reflected spectral light, the collimator A is raised to the position shown in Fig. 5'; the cube C isrotated 90 about the optical axis of the occular as an. axis, to the position shown-in Fig. 5; and the screen D is replaced by the screen E;,, Fig. 5. White light from the collimator A, Fig. 5, falls upon the screen E and the reflected .rays reaching the cube C constitute the unknown light X.. The rest of the operation is as in Case-I.

Case IV. lVit-h purple unknown light, it is necessary to determine the wave-length, not of the dominant hue, but of its complementary The arrangement for emitted purple light is shown in solid lines, Figs. 6 and 7 except that the screen D is. not

used in this case. At L (collimator B) is placed the source whose emitted light X is to'be tested. This unknown li ht X is combined, at the second. face 1 o prism P, with spectral light H from collimator M. White light W from collimator'A enters the cube C, and is matched at E against light X plus light H. The field viewed at E. is shown in Fig. 7. The rest of the operation isas in case I. The result in the case of purple unknownlight is expressed as (1.) the wave-length oat the complementary H of the dominant hue of the unknown X,,; (2) the percentage of-white' impurity, as in .case I; (3) the luminosity, as in case I.

Case V..Wit-h transmit-ted purple light,

a source of white light-is used. at L (col limator B)," and the. unknown light X is the light transmitted from collimator .B

through the screen D, to be tested. The rest are determined, and the result expressed as and (3) a lumlnoslty.

As many changes could be made in the above construction and many apparently (1) a wave-length, (2) -a per cent. white,

widely difl'erent embodiments could be made without departing from the spirit thereof, I intend that all matter contained in the above description or shown in the accompanying drawings shall/be interpreted as illustrative and not in a limiting sense.

Having fully described my invention, what I claim as new and desire .to secure by Letters Patent is: f

1. A method of determining the hue, purity and luminosity of a beam of, light consisting in determining the wave-length of the dominant hue (or ts complementary, as the case may be), the proportion that the white light in the unlmown bears to the pure light of dominant hue therein, and the luminosity of said beam.

2. In combination, means for producing a beam of white light and two beams of colored light, means for matching as to hue and purity either of two of the three beams against the combination of the other two beams, and means for measuring the luminosities of all of said beams.

3. Means for producing a beam of light of unknown color, means for producing a beam of white li ht, means for producing a beam of light oi any desired pure spectral hue, means for adjusting independently the 'intensities of all of said beams, means for combining said last-named beam with either of said first-named beams, and means for matching as to hue and purity the combined beams against the remaining beam.

4. Means for producing a first beam of light of known quality, means for producing a second beam of light, means for producing a third beam of'light, one of the two lastnamed beams being white light and the other being the unknown light, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams. I

. 5. Means for producing a first beam of light of known quality, means for producing a second-beam of light, means for producing a third beam of light, one of the two last-named beams being white light and the other being the unknown light, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams, said a second beam of light, means for producing 7 a third beam of light, one ofthe two lastnamed beams being white light and the other being unknown light, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams, said matching means comprising a photometer cube and observing device.

7. Means for producing a first beam of light of known'quality, means for producing a second beam of light, means for producing a third beam of light, one of the two last named beams being white light and the other being unknown light, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams and means for measuring the luminosity of each beam.

8. Means for producing a first beam of light of known quality, means for producing a second beam of light, means for producing a third beam of light, one of the two lastnamed beams being white light and the other being unknown light, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams and a flicker photometer for measuring the luminosity of each beam.

9. Means for producing a first beam of light of known quality, means for producing a second beam of light, means for producing a third beam of light, one of the two lastnamed beams being white light and the other being unknown light, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams, and a Whitman disk with standard lamp for measuring'the luminosity of each beam.

.10. Means for producing a'first beam of light of known quality, meansfor producing a second beam of light, means for producing a third beam of light, one of the two lastnamed beams being white light and the other being unknown light, means for adjustin independently the luminosities of all of sai beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams.

11. Means for producing a first beam of light of known quality, means for producing a second beam of light, means for producing a third beam of light, one of the two lastnamed beams being white light and the other bein unknown light, means for, adj listing inc ependently the luminosities of all of said beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said light of known quality, means for producing a second beam of-light, means for producing a; third beam of light, one of the two lastnamed beams being white light and the other being unknown light, means for adjusting independently the luminosities of all of said beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said, combined beams, said matching means com? prising a photometer cube and observing de- Z ducing a third beam of light, one of the V1 ce.

13. Means for producing a first beam of lightof known quality, means for producing a .second beam of light, means for producing a third beam of light, one of the two lastnamed beams being white light and the other being unknown light, means for adjusting independently the luminosities of allof said beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams and means for measuring the luminosity of each beam.

14. Means for producing a first beam of light of known quality, means for producing a second beam of light, means for producing a third beam of light, one of the two lastnamed beams being white light and the. other being unknown light, means for adgiusting in- .dependently the luminosities of all of said beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams and a flicker photometer for measuring the luminosity, of each beam.

15. Means for producing a first beam of light of any desired pure spectral hue,

' means for producing a second beam of light,

means for producing a third beam of light, one of the two last-named beams being white light and the other being unknown light, means for adjusting independently the luminosities of all of said beams, means for combining the' first and second beams, means for matching as to hue and purity the third beam against said combined beams. v

16. Means for producing a. first beam of light of any desired pure spectral hue, means for producing a second beam of light, means for producing a third beam of light,

one of the two last-named beams being white light and the other being unknown 4 light, means for combining the first and second beams, .means for matching as to hue and purity the third beam against said com? bined beams and means for measuring the luminosity of each beam.

17. Means for producing a first beam of light of any desired pure spectral hue,

means for producing a second beam of light,

means for producing a third beam of light,

one of the two last-named beams being and means for measuring the luminosity of each beam.

18. Means comprising a dispersing prism for producing a beam of light of any dejsired pure spectral hue, means for producing a second beam of light, means for protwo last-named beams being white light and the other being unknown light, means for combining the first and second beams,

means for matching as to hue and purity the third beam against said combined beams.

19. Means comprising a dispersing prism for producing a beam of light of any desired pure spectral hue, means for producing a second beam of light, means for producing a third beam of light, one of the two last-named beams being white light and the other being unknown light, means for combining the first and second beams, means for matching as to hue and purity thethird beam against said combined beams, and

means for measuring the luminosity of each beam.

20. Means comprising a dispersing prism for producing a beam of light of any desiredpure spectral hue, means for producing a second beam of light, means for producing a third beam of light, one of the two' last-named beams for adjusting independently the luminosities of all of said beams, means for combining the first and second beams, and means for matching as to hue and purity the third beam against said combined beams.

21. Means comprising a dispersing prism for producing a'beamof light of any desired pure spectral hue, means for producing a second beam of light, means for producing a third beam of light, one of the two -last-named beams being white light and the other being unknown light, means for adjusting independently the luminosities of all of said beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams, and means for measuring the luminosity of each beam.

22. Means comprising a dispersin prism and collimator relatively adjustable or producing a first beam of light of any desired pure spectral. hue, means for producing a second beam of light, means for producing a third beam of light, one of the two lastnamed beams being white light and the other being unknown light, means for cobbining the first and second beams, means for matching as to hue and purity the third beam against said combined beams.

23. Means comprising a dispersing prism and collimator relatively adjustable for producing a first beam of light of any desired pure spectral hue, means for producing a means for measuring the luminosity of each beam.-

24. Means comprising a dispersin prism and collimator relatively adjustable or producing a first beam of light of any desired pure spectral hue, means for producing a second beam of light, means for producmg a third beam of light, one of the two lastnamed beams being white light and the other being unknown light, means for adjusting independently the luminosities of all of said beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams.

25. Means comprising a dispersing prism and collimator relatively adjustable for producing a first beam of light of any desired pure spectral hue, means for roduc ing a second beam of 1i ht, .means or producing a third beam of light, one of the two last-named beams being white light and the other being unknown li ht, means for adjusting independently t e luminosities of all of said beams, means for combining the first and second beams, means for matching as to hue and purity the third beam against said combined beams and means for measuring the luminosity of each beam.

In testimony'whereof, I have signed my name to this specification, in the presence of two witnesses.

PERLEY GILMAN NUTTING.

Witnesses:

EDGAR D. TILLYER, LOYD A. J ONES- 

